1. Field of the Invention
The present invention relates to a punching press which employs a servo motor as the drive source for the punching operation.
2. Description of the Related Art
In punching presses, a so-called mechanical crank type driving source is generally used as the driving source for the punching operation. Since the punching operation is the repetition of the short stroke motions, it is considered that the use of a mechanical crank and a flywheel as the driving source for generating the stroke motions is advantageous in terms of the simplification of the mechanism and structure.
In the punching presses which are available in recent years, attempts have been made to finely control the press stroke motions in order to achieve reduction in the punching noises and a punching operation which is suitable to the thickness or material of a blank. However, the control of the press stroke cannot be performed in the mechanical crank type punching press, and hence a mechanism which employs a hydraulic cylinder as the driving source for the punching operation has been proposed. However, the desired punching operation achieved by the use of the hydraulic cylinder requires a large hydraulic power unit. Such a large hydraulic power unit may cause problems involving the operation noises or heat, and hence requires an auxiliary facility, such as a cooling means or noise cover, thus requiring an large installation space for the auxiliary facility. Also, the hydraulic control system has a complicated structure, and it is thus difficult to achieve the control operation which has excellent responsibility.